The (really) inside story: Are cattle meant to eat grain? It's a contentious debate and Greg Penner is putting the facts on the table

Naturally raised beef is all the rage these days. After all, cows meandering in pastures make for prettier pictures than those huddled in feedlot pens.

Glenn CheaterApr 30, 2015 1:00 AM

But critics of ‘industrial farming’ also argue Mother Nature designed cows to forage, and that a grain diet is unnatural and leads to serious health problems.

A condition called acidosis is at the heart of this criticism. The ruminant version of heartburn, acidosis is typically sparked by eating feed high in starch or sugar, which results in a sharp drop in pH. Low pH is acidic, and repeated bouts of acute acidosis can result in nasty outcomes — such as liver abscesses and lameness — that fuel criticism of feeding cattle grain.

But research by Greg Penner is shining a new light on the ‘cattle weren’t meant to eat grain’ debate.

“Actually, we can’t say acidosis is an issue only caused by feeding grain,” says the associate professor of animal and poultry science. “People perceive grass as being more beneficial, but acidosis can occur in grazing cattle when there’s lots of sugar in the grass.”

That fact has been known for a long time. But Penner, whose work in ruminant nutritional physiology earned him the award of a Centennial Enhancement Chair earlier this year, is delving much deeper than past researchers could.

It’s a story that starts with a very clever invention he created as a Masters student and ends with insights into how cows share a bad human habit that comedian Louis C.K. calls “eating until I hate myself.”

But first, Penner’s cool invention.

Researchers have long measured pH via a process called fistulation, in which a removable plastic device (called a cannula) is surgically inserted into the side of an animal allowing access to the rumen. It’s not the most pleasant way to measure pH and has a serious drawback — acid levels in the rumen can fluctuate dramatically in a matter of minutes. So it’s not easy to get a true picture of what’s happening if you have to physically collect a sample for every test.

By the time Penner was taking his Masters in 2005, the process had been automated — but there was a catch.

“Automatic pH measurement required the cow to be hardwired to a data logger and the data logger hardwired to a computer,” he says. “I needed to be able to measure pH in an animal that wasn’t tied up in a stall, so I was looking for a way to get rid of those cords.”

His solution was to buy some compact data loggers and put them in a water-tight capsule. It worked so well, other researchers wanted them and Penner asked a company to manufacture some. The company recognized there was a global market for the device and has since sold about 500.

“My mistake was not getting licensing rights,” Penner says with a laugh.

But the loss in royalties was offset by a big leap forward in research capability. Fistulated animals require special care and so they’re kept at research facilities. But Penner’s device could be used in a commercial feedlot — the cow simply swallows the small device, which is retrieved from the rumen once the animal is slaughtered and its data downloaded.

This allowed real-world testing. Using this new technology, Penner measured the pH levels in the rumen of 30 feedlot steers with measurements occurring every 15 minutes until the cattle were slaughtered 141 days later. Penner expected the test would confirm a rich grain diet causes frequent bouts of acidosis.

“Based on the literature, we had some preconceived notions as we went in,” he says. “We thought the greatest risk would be as we transitioned cattle from a forage diet to the high grain finishing diet, and then maybe again at the end at the finishing when they’ve been on the grain diet for a long time. But that wasn’t really the case.”

The study found the feedlot steers, on average, were experiencing acidosis one to two hours per day — far below the six to 20 hours a day that earlier studies had recorded.

So why the difference?

It will take further investigation to definitively answer that question, but there’s a big and obvious difference between a feedlot and a research facility.

“Most of the previous studies would have housed animals individually in a pen, so they could make very detailed measurements on each individual,” says Penner. “What we think is happening is that when you house an animal by itself, they change their eating habits.”

It’s a little like the difference between a big family dinner and binge-eating, Louis C.K.-style. It turns out feedlot cattle don’t simply stick their head in the trough and eat until they’re stuffed. They mill about and have continuous bovine interactions, including the old favourite of bumping another steer out of the way because the animal decides it wants that exact spot at the feed bunk.

However, a cow or steer by itself appears to eat more out of boredom.

“That seems to be the case,” says Penner. “Intake is a bit higher, even when we put in, for a lack of a better term, toys for the animals to play with and also give them nose-to-nose contact with other animals so they’re not socially isolated. It’s just different.”

The study shows feedlot operators are doing a better job than they’ve been given credit for, he says, but also opens the door to further improvements. It’s common practice to re-sort animals in the feedlot to keep ones of the same weight, for example, in one pen. But that may disrupt feeding patterns, as it takes a while for a new social hierarchy to be established, notes Penner.

“We think that may be another risk factor, although we haven’t been able to test that yet.”

Penner’s research wasn’t designed to settle the grass-versus-grain debate. But it is replacing conjecture with hard scientific data.

“I’m not advocating either — there are pros and cons to each,” he says. “But I think people need to understand the amount of forage you need to produce a kilo of beef is very large relative to cereal grains. Feeding a high-grain diet allows us to improve efficiency in cattle production.

“And when I talk about efficiency, I’m also talking about animal welfare, because that is a key part of it.”